Systems, Methods, and Apparatus to Preheat Welding Wire

ABSTRACT

Systems, methods, and apparatus to preheat weld wire are disclosed. An example contact tip includes: an inner bore configured to conduct current to a consumable welding electrode; screw threads on an exterior of the contact tip; and a head opposite the screw threads on an exterior of the contact tip to enable threading and dethreading of the contact tip.

RELATED APPLICATIONS

This patent is a continuation of U.S. patent application Ser. No.16/005,461, filed Jun. 11, 2018, entitled “Systems, Methods, andApparatus to Preheat Welding Wire,” and claims priority to U.S.Provisional Patent Application Ser. No. 62/517,541, filed Jun. 9, 2017,entitled “Systems, Methods, and Apparatus to Preheat Welding Wire.” Theentireties of U.S. patent application Ser. No. 16/005,461 and U.S.Provisional Patent Application Ser. No. 62/517,541 are incorporatedherein by reference.

BACKGROUND

This disclosure relates generally to welding and, more particularly, towelding torches and methods to provide wire preheating for welding.

Welding is a process that has increasingly become ubiquitous in allindustries. Welding is, at its core, simply a way of bonding two piecesof metal. A wide range of welding systems and welding control regimeshave been implemented for various purposes. In continuous weldingoperations, metal inert gas (MIG) welding and submerged arc welding(SAW) techniques allow for formation of a continuing weld bead byfeeding welding wire shielded by inert gas from a welding torch and/orby flux. Such wire feeding systems are available for other weldingsystems, such as tungsten inert gas (TIG) welding. Electrical power isapplied to the welding wire and a circuit is completed through theworkpiece to sustain a welding arc that melts the electrode wire and theworkpiece to form the desired weld.

While very effective in many applications, these welding techniques mayexperience different initial welding performance based upon whether theweld is started with the electrode “cold” or “hot.” In general, a coldelectrode start may be considered a start in which the electrode tip andadjacent metals are at or relatively near the ambient temperature. Hotelectrode starts, by contrast, are typically those in which theelectrode tip and the adjacent metals' temperature are much moreelevated, but below the melting point of the electrode wire. In someapplications, it is believed that initiation of welding arcs and weldsis facilitated when the electrode is hot. However, the current state ofthe art does not provide regimes designed to ensure that the electrodeis heated prior to initiation of a welding operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example robotic welding system in which a robot isused to weld a workpiece using a welding tool, in accordance withaspects of this disclosure.

FIG. 2 illustrates an example liquid-cooled welding torch, in accordancewith aspects of this disclosure.

FIG. 3 illustrates an exploded view of the example liquid-cooled weldingtorch of FIG. 2 .

FIG. 4 is a more detailed depiction of an example liquid coolingassembly that may be used to implement the liquid cooling assemblies ofFIG. 2 .

FIG. 5 is a cross-section view of the liquid-cooled power cable assemblyof FIG. 4 .

FIG. 6 is an exploded view of the example liquid-cooled power cableassembly of FIG. 3 .

FIGS. 7A, 7B, and 7C are views of the example cooler body of FIG. 6 .

FIG. 8 is a cross-section view of the liquid cooling assembly and thequick-disconnect assembly of FIG. 2 coupled to the liquid coolingassembly of FIG. 4 .

FIG. 9 illustrates the example welding assembly and the example liquidcooling assemblies of FIG. 2 disconnected from the remainder of thetorch via the quick-disconnect assembly.

FIG. 10 is a cross-section view of the example welding assembly of FIG.2 .

FIGS. 11A, 11B, and 11C show an example implementation of the firstcontact tip of FIG. 10 .

FIGS. 12A and 12B show an example implementation of the wire guide ofFIG. 10 .

FIGS. 13A, 13B, and 13C show an example implementation of the secondcontact tip of FIG. 10 .

FIGS. 14A and 14B illustrate views of the example diffuser of FIGS. 3and 10 .

FIG. 15A illustrates a conventional robotic welding torch having a firsttool center point distance and torch neck angle, in accordance withaspects of this disclosure.

FIG. 15B illustrates an example implementation of the liquid-cooledwelding torch of FIG. 2 configured to replace the conventional torch ofFIG. 15A while maintaining a same tool center point distance and torchneck angle.

FIG. 16 is a cross section of an example welding cable that may be usedto provide cooling liquid, welding current, and preheating current to awelding torch, and to carry cooling liquid away from the welding torch,in accordance with aspects of this disclosure.

FIG. 17 illustrates a functional diagram of an example welding systemincluding the example welding torch of FIG. 2 , and which may be usedwith the welding system of FIG. 1 .

FIG. 18 is a block diagram of an example implementation of the powersupplies of FIG. 17 .

FIG. 19 illustrates another example liquid-cooled welding torch, inaccordance with aspects of this disclosure.

FIG. 20 is an exploded view of the example welding torch of FIG. 19 .

FIG. 21 is a cross-sectional plan view of the example welding assemblyof FIG. 19 .

FIG. 22 is a cross-sectional plan view of the example power and liquidtransfer assembly of FIG. 19 .

FIG. 23 is a view of the example power and liquid transfer assembly ofFIG. 19 .

The figures are not to scale. Where appropriate, the same or similarreference numerals are used in the figures to refer to similar oridentical elements.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of thisdisclosure, reference will be now made to the examples illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theclaims is intended by this disclosure. Modifications in the illustratedexamples and such further applications of the principles of thisdisclosure as illustrated therein are contemplated as would typicallyoccur to one skilled in the art to which this disclosure relates.

As used herein, the word “exemplary” means “serving as an example,instance, or illustration.” The embodiments described herein are notlimiting, but rather are exemplary only. It should be understood thatthe described embodiments are not necessarily to be construed aspreferred or advantageous over other embodiments. Moreover, the terms“embodiments of the invention,” “embodiments,” or “invention” do notrequire that all embodiments of the invention include the discussedfeature, advantage, or mode of operation.

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (code) that may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing a first set of one or more lines of codeand may comprise a second “circuit” when executing a second set of oneor more lines of code. As utilized herein, “and/or” means any one ormore of the items in the list joined by “and/or”. As an example, “xand/or y” means any element of the three-element set {(x), (y), (x, y)}.In other words, “x and/or y” means “one or both of x and y.” As anotherexample, “x, y, and/or z” means any element of the seven-element set{(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, “x,y, and/or z” means “one or more of x, y and z”. As utilized herein, theterm “exemplary” means serving as a non-limiting example, instance, orillustration. As utilized herein, the terms “e.g.” and “for example” setoff lists of one or more non-limiting examples, instances, orillustrations. As utilized herein, circuitry is “operable” to perform afunction whenever the circuitry comprises the necessary hardware andcode (if any is necessary) to perform the function, regardless ofwhether performance of the function is disabled or not enabled (e.g., byan operator-configurable setting, factory trim, etc.).

As used herein, a wire-fed welding-type system refers to a systemcapable of performing welding (e.g., gas metal arc welding (GMAW), gastungsten arc welding (GTAW), etc.), brazing, cladding, hardfacing,and/or other processes, in which a filler metal is provided by a wirethat is fed to a work location, such as an arc or weld puddle.

As used herein, a welding-type power source refers to any device capableof, when power is applied thereto, supplying welding, cladding, plasmacutting, induction heating, laser (including laser welding and lasercladding), carbon arc cutting or gouging and/or resistive preheating,including but not limited to transformer-rectifiers, inverters,converters, resonant power supplies, quasi-resonant power supplies,switch-mode power supplies, etc., as well as control circuitry and otherancillary circuitry associated therewith.

As used herein, preheating refers to heating the electrode wire prior toa welding arc and/or deposition in the travel path of the electrodewire.

As used herein, the terms “front” and/or “forward” refer to locationscloser to a welding arc, while “rear,” “back,” “behind,” and/or“backward” refers to locations farther from a welding arc.

Some disclosed examples describe electric currents being conducted“from” and/or “to” locations in circuits and/or power supplies.Similarly, some disclosed examples describe “providing” electric currentvia one or more paths, which may include one or more conductive orpartially conductive elements. The terms “from,” “to,” and “providing,”as used to describe conduction of electric current, do not necessitatethe direction or polarity of the current. Instead, these electriccurrents may be conducted in either direction or have either polarityfor a given circuit, even if an example current polarity or direction isprovided or illustrated.

Disclosed example contact tips include: an inner bore configured toconduct current to a consumable welding electrode; screw threads on anexterior of the contact tip; and a head opposite the screw threads on anexterior of the contact tip to enable threading and dethreading of thecontact tip. In some examples, the screw threads include longitudinalslots to permit welding gas to flow along an exterior of the contacttip. In some examples, the head has a hexagonal cross-section. In someexamples, the inner bore extends through the head. In some examples, thehead has a smaller diameter than a major diameter of the screw threads.

Some example contact tips further include a second bore having a largerdiameter than the inner bore and located on a rear side of the contacttip of the inner bore. Some example contact tips further include acontact insert in the inner bore and configured to contact theconsumable welding electrode.

Disclosed example welding torches include: a first contact tipconfigured to conduct welding current to a consumable welding electrodetraveling through the first contact tip at a first location in thewelding torch; and a second contact tip configured to conduct weldingcurrent to the consumable welding electrode at a second location in thewelding torch, in which the second contact tip includes: an inner boreconfigured to conduct the current to the consumable welding electrode;screw threads on an exterior of the contact tip; and a head opposite thescrew threads on an exterior of the preheating contact tip to enableattachment and detachment of the preheating contact tip via a tip of anozzle assembly.

In some examples, the screw threads have longitudinal slots to permitwelding gas to flow along an exterior of the contact tip. Some examplewelding torches further include a diffuser configured to: receive thefirst contact tip and conduct the welding current to the first contacttip; receive the welding gas from the second contact tip; and output thewelding gas to a nozzle for delivery to a welding operation. In someexamples, the head has a hexagonal cross-section. In some examples, theinner bore extends through the head. In some examples, the head has asmaller diameter than a major diameter of the screw threads.

In some example welding torches, the second contact tip further includesa second bore having a large diameter than the inner bore and located ona rear side of the second contact tip of the inner bore. Some examplewelding torches further include a torch neck having internal threads andconfigured to receive the second contact tip. Some example weldingtorches further include a wire guide configured to guide the consumablewelding electrode between the first contact tip and the second contacttip.

Disclosed example contact tips include: an inner bore configured toconduct current to a consumable welding electrode; screw threads on anexterior of the contact tip, wherein the screw threads compriselongitudinal slots to permit welding gas to flow along an exterior ofthe contact tip. Some example contact tips further include a head on anexterior of the contact tip to enable threading and dethreading of thecontact tip. Some example contact tips further include a second borehaving a larger diameter than the inner bore and located on a rear sideof the contact tip of the inner bore. Some example contact tips furtherinclude a contact insert in the inner bore and configured to contact theconsumable welding electrode.

Referring to FIG. 1 , an example welding system 100 is shown in which arobot 102 is used to weld a workpiece 106 using a welding tool 108, suchas the illustrated bent-neck (i.e., gooseneck design) welding torch (or,when under manual control, a handheld torch), to which power isdelivered by welding equipment 110 via conduit 118 and returned by wayof a ground conduit 120. The welding equipment 110 may comprise, interalia, one or more power sources (each generally referred to herein as a“power supply”), a source of a shield gas, a wire feeder, and otherdevices. Other devices may include, for example, water coolers, fumeextraction devices, one or more controllers, sensors, user interfaces,communication devices (wired and/or wireless), etc.

The welding system 100 of FIG. 1 may form a weld (e.g., at weld joint112) between two components in a weldment by any known electric weldingtechniques. Known electric welding techniques include, inter alia,shielded metal arc welding (SMAW), MIG, flux-cored arc welding (FCAW),TIG, laser welding, sub-arc welding (SAW), stud welding, friction stirwelding, and resistance welding. MIG, TIG, hot wire cladding, hot wireTIG, hot wire brazing, multiple arc applications, and SAW weldingtechniques, inter alia, may involve automated or semi-automated externalmetal filler (e.g., via a wire feeder). In multiple arc applications(e.g., open arc or sub-arc), the preheater may pre-heat the wire into apool with an arc between the wire and the pool. The welding equipment110 may be arc welding equipment having one or more power supplies, andassociated circuitry, that provides a direct current (DC), alternatingcurrent (AC), or a combination thereof to an electrode wire 114 of awelding tool (e.g., welding tool 108). The welding tool 108 may be, forexample, a TIG torch, a MIG torch, or a flux cored torch (commonlycalled a MIG “gun”). The electrode wire 114 may be tubular-typeelectrode, a solid type wire, a flux-core wire, a seamless metal corewire, and/or any other type of electrode wire.

As will be discussed below, the welding tool 108 employs a contact tipassembly that heats the electrode wire 114 prior to forming a weldingarc using the electrode wire 114. Suitable electrode wire 114 typesincludes, for example, tubular wire, metal cored wire, aluminum wire,solid gas metal arc welding (GMAW) wire, composite GMAW wire,gas-shielded FCAW wire, SAW wire, self-shielded wire, etc.

In the welding system 100, the robot 102, which is operatively coupledto welding equipment 110 via conduit 118 and ground conduit 120,controls the location of the welding tool 108 and operation of theelectrode wire 114 (e.g., via a wire feeder) by manipulating the weldingtool 108 and triggering the starting and stopping of the current flow(whether a preheat current and/or welding current) to the electrode wire114 by sending, for example, a trigger signal to the welding equipment110. When welding current is flowing, a welding arc is developed betweenthe electrode wire 114 and the workpiece 106, which ultimately producesa weldment. The conduit 118 and the electrode wire 114 thus deliverwelding current and voltage sufficient to create the electric weldingarc between the electrode wire 114 and the workpiece 106. At the pointof welding between the electrode wire 114 and the workpiece 106, thewelding arc locally melts the workpiece 106 and electrode wire 114supplied to the weld joint 112, thereby forming a weld joint 112 whenthe metal cools.

In certain aspects, in lieu of a robot 102's robotic arm, a humanoperator may control the location and operation of the electrode wire114. For example, an operator wearing welding headwear and welding aworkpiece 106 using a handheld torch to which power is delivered bywelding equipment 110 via conduit 118. In operation, as with the system100 of FIG. 1 , an electrode wire 114 delivers the current to the pointof welding on the workpiece 106 (e.g., a weldment). The operator,however, could control the location and operation of the electrode wire114 by manipulating the handheld torch and triggering the starting andstopping of the current flow via, for example, a trigger. A handheldtorch generally comprises a handle, a trigger, a conductor tube, anozzle at the distal end of the conductor tube, and a contact tipassembly. Applying pressure to the trigger (i.e., actuating the trigger)initiates the welding process by sending a trigger signal to the weldingequipment 110, whereby welding current is provided, and the wire feederis activated as needed (e.g., to drive the electrode wire 114 forward tofeed the electrode wire 114 and in reverse to retract the electrode wire114). Commonly owned U.S. Pat. No. 6,858,818 to Craig S. Knoener, forexample, describes an example system and method of controlling a wirefeeder of a welding-type system.

FIG. 2 illustrates an example liquid-cooled welding torch 200. Theliquid-cooled welding torch 200 may be used to implement the weldingtool 108 of FIG. 1 to deliver the electrode wire 114 to a workpiecewhile providing both resistive preheating power and welding-type power.

The liquid-cooled welding torch 200 includes a welding assembly 202, amounting assembly 204, a weld cable 206, liquid cooling assemblies 208,210, 212, 214, and a power and liquid transfer assembly 216. Asdisclosed herein, the example liquid-cooled welding torch 200 may beused to replace conventional robotic welding torches with resistivepreheating-enabled welding torches having a same tool center point(TCP). By replacing a torch with another torch having a same TCP, therobot may be capable of continuing a welding program using thereplacement torch with little or no reprogramming of tool points.

The welding assembly 202 receives weld current and preheating current,conducts the weld current to the electrode wire 114, and conducts thepreheating current through a portion of the electrode wire 114. Theexample welding assembly 202 is liquid-cooled by liquid provided via theliquid cooling assemblies 208-214. The example welding assembly 202 ofFIG. 2 receives the weld current via one or more of the weld cable 206,the liquid cooling assemblies 208 and 212, and/or the liquid coolingassemblies 210 and 214. Because the workpiece provides the return pathfor the weld current to the power supply, no return path is provided viathe weld cable 206 or the liquid cooling assemblies 208. The weld cable206 is an air-cooled (or gas-cooled) cable. However, the weld cable 206may also be liquid-cooled.

The example welding assembly 202 receives the preheating current via theweld cable 206, the liquid cooling assemblies 208 and 212, and/or theliquid cooling assemblies 210 and 214. In the example of FIG. 2 , theweld current is conducted via a different one of the weld cable 206, theliquid cooling assemblies 208 and 212, or the liquid cooling assemblies210 and 214 than the preheating current that has the same polarity(i.e., current flow direction). The welding assembly 202 conducts thepreheating current through a section of the electrode wire 114 to heatthe electrode wire via resistive heating (e.g., FR heating). The preheatcurrent then returns to a preheating power supply via a different one ofweld cable 206, the liquid cooling assemblies 208 and 212, or the liquidcooling assemblies 210 and 214 to complete a preheating circuit.

In the example of FIG. 2 , the weld current path, the preheating currentsupply path, and the preheating current return path may all be differentones of the weld cable 206, the liquid cooling assemblies 208 and 212,and the liquid cooling assemblies 210 and 214. In some examples, theweld current path may be superimposed with the preheating current supplypath or the preheating current return path to reduce the net current inthe conductor. For example, if the weld current is 300 A and thepreheating current is 100 A, the weld current and the preheating currentmay be superimposed to result in a net current of 200 A.

As described in more detail below, the welding assembly 202 and theliquid cooling assemblies 212, 214 may be separated from the remainderof the liquid-cooled welding torch 200 via the power and liquid transferassembly 216.

FIG. 3 illustrates an exploded view of the example liquid-cooled weldingtorch 200 of FIG. 2 .

As shown in FIG. 3 , the example welding assembly 202 includes a nozzle302, a diffuser insulator 304, a first contact tip 306, a wire guide308, a gas diffuser 310, a first contact tip insulator 312, a secondcontact tip 314, a second contact tip insulator 316, a nozzle mount 318,and a nozzle mount clamp 320.

A liquid-cooled power cable assembly 322 includes the liquid coolingassemblies 212, 214, a cooler 324, and power connector pins 326, 328.The liquid-cooled power cable assembly 322 is described below in moredetail with reference to FIGS. 6, 7A, 7B, and 8 .

The power and liquid transfer assembly 216 enables quick separation ofthe welding assembly 202 and the liquid-cooled power cable assembly 322from the mounting assembly 204. In the example of FIG. 3 , the power andliquid transfer assembly 216 includes a saddle 330, a saddle cover 332,a saddle clasp 334, and saddle clamps 336. The power and liquid transferassembly 216 is described below in more detail with reference to FIGS. 4and 5 .

The example mounting assembly 204 includes a torch body 338, a neck 340,and a robot link assembly 342 including, for example, a bracket, a linkarm, and a robot mounting disk.

FIG. 4 is a more detailed depiction of an example liquid coolingassembly 400 that may be used to implement the liquid cooling assemblies208, 210 of FIG. 2 . FIG. 5 is a cross-section view of the liquidcooling assembly 400 of FIG. 4 .

The liquid cooling assembly 400 includes a power cable socket 402 thatholds a power transfer socket 404 and a liquid shutoff valve 406. Theliquid cooling assembly 400 also includes a hose 408 and an internalconductor 410. The hose 408 is coupled to the power cable socket 402 ona first end and coupled to a power cable fitting 412 on a second end.

The power cable socket 402 receives one of the power connector pins 326,328 to transfer cooling liquid and welding current and/or preheatingcurrent to a corresponding one of the liquid cooling assemblies 212,214. The power transfer socket 404 enables insertion of the powerconnector pin 326, 328, and transfers current to and/or from an insertedpower connector pin 326, 328. An example power transfer socket that maybe used to implement the power transfer socket 404 is a PowerBud® powercontact, sold by Methode Electronics, Inc., which provides multiplecontact points between the power transfer socket and an inserted powerconnector pin 326, 328.

The liquid shutoff valve 406 selectively permits flow of liquid from thehose 408 to the power transfer socket 404 and to a connected liquidcooling assembly 212, 214. The example liquid shutoff valve 406 is aSchrader valve. However, other types of valves may be used to implementthe liquid shutoff valve 406. When a power connector pin 326, 328 isinserted (e.g., fully inserted) into the power transfer socket 404, thepower connector pin 326, 328 displaces (e.g., unseats) a stem 414 from acore 416 of the valve 406, which permits liquid to flow to and/or fromthe hose 408. When the power connector pin 326, 328 is removed orpartially removed, the stem 414 is forced back into the core 416 andstops flow of liquid.

The hose 408 is coupled to the power cable fitting 412 via a ferrule 418and a fitting nut 420. The power cable fitting 412 is coupled to asource of weld current and/or preheating current, and is electricallyconnected to transfer the weld current and/or preheating current to orfrom the internal conductor 410 of the hose 408. The hose 408 is alsocoupled to the power cable socket 402 via a ferrule 418. The examplepower cable fitting 412, the example power cable socket 402, and/or thehose 408 include hose barbs to secure the hose 408. However, othermethods of securing the hose to the power cable fitting 412 and/or thepower cable socket 402 may be used, such as clamps, compressionfittings, or any other hose fittings.

During operation, when the power cable fitting 412 is coupled to a powersource and a liquid cooling device, and the power cable socket 402 iscoupled to a liquid cooling assembly 212, 214, the example liquidcooling assembly 400 permits liquid to flow through the power cablefitting 412, the hose 408, the valve 406, the power cable socket 402,and the power transfer socket 404, either to or from the liquid coolingdevice (e.g., based on whether the assembly is configured as the liquidsupply or the liquid return). The example liquid cooling assembly 400also conducts current from and/or to a weld power supply and/or apreheating power supply. For example, the current is conducted throughthe power cable fitting 412, the internal conductor 410, the power cablesocket 402, and the power transfer socket 404.

FIG. 6 is an exploded view of the example liquid-cooled power cableassembly 322 of FIG. 3 . The liquid-cooled power cable assembly 322provides cooling liquid supply and return paths from the liquid coolingassemblies 212, 214 to the welding assembly 202 of FIG. 3 . Theliquid-cooled power cable assembly 322 includes the liquid coolingassemblies 212, 214, the power connector pins 326, 328, a cooling body602, and a cooling body cover 604.

Each of the example liquid cooling assemblies 212, 214 includes threelayers: an inner conductive layer 606 a, 606 b; an insulative layer 608a, 608 b; and an outer protective layer 610 a, 610 b. The innerconductive layer 606 a, 606 b conduct current and liquid, and isconstructed of a conductive material such as copper. The insulativelayers 608 a, 608 b provide electrical insulation between the innerconductive layers 606 a, 606 b and the outer protective layers 610 a,610 b. The example insulative layers 608 a, 608 b may be silicone, PTFE,PET, and/or any other suitable electrically insulative material orcombination of materials. The outer protective layers 610 a, 610 bprovide rigidity and/or physical protection from damage, such aspunctures. The outer protective layers 610 a, 610 b may be a rigidmaterial such as aluminum or any other appropriate material orcombination of materials.

In some examples, two or more of the layers 606 a-610 a, 606 b-610 b maybe combined. For example, the insulative layers 608 a, 608 b may alsoserve as the outer protective layers 610 a, 610 b, or vice versa. Inother examples, the outer protective layers 610 a, 610 b may be omitted.

The inner conductive layers 606 a, 606 b are contained within theinsulative layers 608 a, 608 b. The insulative layers 608 a, 608 b aresimilar contained within the outer protective layers 610 a, 610 b.

One of the liquid cooling assemblies 212, 214 supplies cooling liquid tothe cooling body 602, and the other of the liquid cooling assemblies212, 214 receives the liquid from the cooling body 602. The cooling body602 circulates the liquid through a tortuous path 612 between a liquidinput port and a liquid output port. The cooling body 602 is coupled tothe welding assembly 202 to conduct heat from the components in thewelding assembly 202 to the liquid, thereby cooling the welding assembly202. The cooling body cover 604 is attached to the cooling body 602 tocontain the fluid within the tortuous path 606. In some examples, thecooling body 602 and a cooling body cover 604 may be a single unit(e.g., constructed using additive manufacturing techniques).

FIGS. 7A, 7B, and 7C are views of the example cooler body 602 of FIG. 6. As illustrated in FIGS. 7A, 7B, and 7C, the tortuous path 612 includesa continuous path around a circumference of the cooler body 602. In theillustrated example, the liquid cooling assembly 214 supplies coolingliquid to the cooler body 602 and the liquid cooling assembly 212returns the cooling liquid to a liquid cooler. The cooling liquidfollows a flow path 702 (shown using a dotted line) through the tortuouspath 612 to increase heat transfer from the welding assembly 202 to theliquid. Continuities A and B from one view to the next are shown inFIGS. 7A, 7B, and 7C.

FIG. 8 is a cross-section view of the liquid cooling assembly 212, 214and the power and liquid transfer assembly 216 of FIG. 2 coupled to theliquid cooling assembly 400 of FIG. 4 .

As illustrated in FIG. 8 , the power cable socket 402 is seated in thesaddle 330, which prevents movement of the power cable socket 402. Theexample power connector pin 326 is inserted into the power cable socket402 and the power transfer socket 404. The power connector pin 326includes an inner liquid coolant passage 802, one or more liquid coolantports 804 to enable liquid to flow into and/or out of the liquid coolantpassage 802, and a seal 806. When inserted, the power connector pin 326opens the valve 406 to permit liquid to flow through the valve 406, theliquid coolant ports 804, the liquid coolant passage 802, and the innerconductive layer 606 a. A retaining ring 808 may be included in thesaddle cover 332 to hold the power connector pin 326 in place.

In addition to placing the liquid cooling assembly 212 in fluidcommunication with the liquid cooling assembly 208, the example powerconnector pin 326 also conducts weld current and/or preheating currentbetween the liquid cooling assembly 212 and the liquid cooling assembly208. The example inner conductive layer 606 a is in electrical contactwith the power transfer pin 326, which is a conductive material (e.g.,copper) and is in electrical contact with the power transfer socket 404.

While the examples are described with reference to the liquid coolingassembly 208, the liquid cooling assembly 212, and the power connectorpin 326, these examples are similarly applicable to the liquid coolingassembly 210, the liquid cooling assembly 214, and the power connectorpin 328.

FIG. 9 illustrates the example welding assembly 202 and the exampleliquid cooling assemblies 212, 214 of FIG. 2 disconnected from theremainder of the torch 200 via the power and liquid transfer assembly216. For detachment of the example liquid cooling assemblies 212, 214,the example saddle clasp 334 is unhooked or otherwise detached from aretention pin 902 on the saddle 330. When the saddle clasp 334 isunhooked, the power connector pin 328 can be disengaged from the powercable socket 402 and the saddle cover 332 can be simultaneously liftedfrom the saddle 330. Conversely, to install the liquid coolingassemblies 212, 214, the power connector pins 326, 328 are inserted intocorresponding power cable sockets 402 while the saddle cover 332 isplaced onto the saddle 330. When the power connector pins 326, 328 andthe saddle cover 332 are in place on the saddle 330, the saddle clasp334 is hooked into the retention pin 902 to hold the power connectorpins 326, 328 in place.

FIG. 10 is a cross-section view of the example welding assembly 202 ofFIG. 2 . The welding assembly 202 is liquid-cooled via the liquidcooling assemblies 212, 214. The liquid cooling assemblies 212, 214and/or a torch neck 1002 provide weld current and preheating current tothe welding assembly 202 for preheating the electrode wire 114 and forgenerating a welding arc.

The example welding assembly 202 includes the nozzle 302, the diffuserinsulator 304, the first contact tip 306, the wire guide 308, the gasdiffuser 310, the first contact tip insulator 312, the second contacttip 314, the second contact tip insulator 316, the nozzle mount 318, thenozzle mount clamp 320, the cooling body 602, and the cooling body cover604. The welding assembly 202 is attached to a torch neck 1002, throughwhich a wire liner 1004 conveys the electrode wire 114 and/or shieldinggas to the welding assembly 202.

The first contact tip 306 delivers welding current to the electrode wire114 for arc welding. The first contact tip 306 is threaded into a gasdiffuser 310, which is in turn threaded into the diffuser insulator 304.The diffuser insulator 304 provides electrical and thermal insulationbetween the gas diffuser 310 and the nozzle 302.

The gas diffuser 310 is threaded into the cooling body 602. The coolingbody 602 conducts welding current and/or preheating current from theliquid-cooled power cable assembly 322 (e.g., from the inner conductivelayer(s) 606 a, 606 b) to the diffuser 310, which is electricallyconnected to the first contact tip 306. The first contact tip insulator312 and the diffuser insulator 304 provide electrical insulation betweenthe weld current and preheat current path(s) and the nozzle 302.

The second contact tip 314 is electrically coupled to the torch neck1002 to conduct preheating current to and/or from the electrode wire114. The preheating circuit includes the torch neck 1002, the secondcontact tip 314, the first contact tip 306, a portion of the electrodewire 1006 between the second contact tip 314 and the first contact tip306, the diffuser 310, the cooling body 602, and one or both of theinner conductive layers 606 a, 606 b in the liquid-cooled power cableassembly 322.

The second contact tip insulator 316 provides electrical insulationbetween the second contact tip 314 and the cooling body 602. The secondcontact tip insulator 316 includes a seal 1008 (e.g., an o-ring) toreduce or prevent welding gas leakage.

The nozzle mount 318 and the nozzle mount clamp 320 provide anattachment point for threading the welding assembly 202 onto the torchneck 1002. The nozzle mount 318 physically couples and/or providessupport to the liquid-cooled power cable assembly 322 from the torchneck 1002, which is rigid.

In addition to the welding assembly 202, the liquid-cooled power cableassembly 322, and the torch neck 1002 being detachable from the mountingassembly 204 (e.g., via the power and liquid transfer assembly 216 and aconventional disconnection feature between the torch neck 1002 and themounting assembly 204), the welding assembly 202 may be completely orpartially disassembled to access one or more of the components in thewelding assembly 202.

In the example of FIG. 10 , the first contact tip 306, the wire guide308, and/or the second contact tip 314 are removable via the tip of thenozzle 302. FIGS. 11A, 11B, and 11C show an example implementation ofthe first contact tip 306, FIGS. 12A and 12B show an exampleimplementation of the wire guide 308, and FIGS. 13A, 13B, and 13C showan example implementation of the second contact tip 314.

As shown in FIGS. 10 and 11A, a first end 1102 of the first contact tip306 has a hexagonal cross-section. The hexagonal cross-section enablesthe first contact tip 306 to be unthreaded from the diffuser 310 via theopening in the nozzle 302. Other exterior geometries may be used for thecross-section of the first end 1102 of the first contact tip 306.Additionally or alternatively, an interior geometry may be used (e.g.,in combination with a corresponding tool) to unthread the first contacttip 306 from the diffuser 310.

After removal of the first contact tip 306 from the welding assembly 202via the nozzle 302, the wire guide 308 may also be removed via thenozzle 302. As shown in FIGS. 10, 12A, and 12B, an outer surface 1202 ofthe wire guide 308 is relatively smooth (e.g., not threaded) and can beinserted into and removed from of an inner diameter 1010 of the coolingbody 602 without threading. The wire guide 308 has a wire path 1204 toguide the wire from the second contact tip 314 to the first contact tip306. In some examples, the wire guide 308 is a nonconductive materialsuch as ceramic, so that the electrode wire 114 is the only conductivepath between the second contact tip 314 and the first contact tip 306.

As shown in FIGS. 13A, 13B, and 13C, the second contact tip 314 includesa hexagonal cross-section on a first end 1302 of the second contact tip314. An interior surface 1304 and/or an exterior surface 1306 (e.g., ahead) of the first end 1302 may provide the hexagonal cross-sectionand/or any other shape that enables the second contact tip to beunthreaded from the torch neck 1002. The example second contact tip 314includes threads 1305 to enable the second contact tip 314 to bethreaded into the second contact tip insulator 316. The exterior surface1306 has a smaller diameter than the major diameter of the threads 1305,which can improve access to the exterior surface 1306 for removal and/orinstallation of the second contact tip 314.

As shown in FIG. 10 , the outer diameter of the second contact tip 314is equal to or less than the inner diameter 1010 of the cooling body 602and less than an inner diameter 1012 of the second contact tip insulator316 to enable the second contact tip 314 to be removed via the tip ofthe nozzle 302, the cooling body 602, and the second contact tipinsulator 316. The first end 1302 may be manipulated (e.g., via a toolinserted through the nozzle 302) to unthread the second contact tip 314from the torch neck 1002, after which the second contact tip 314 can beremoved from the welding assembly 202 without disassembly of the weldingassembly 202.

As shown in FIGS. 13A, 13B, and 13C, the second contact tip 314 includesslots 1308 running longitudinally on the exterior of the second contacttip 314 through the threads 1305. The slots 1308 permit the flow ofwelding gas from the interior of the torch neck 1002 to the diffuser 310via the cooling body 602 (e.g., through the interior of the cooling body602 through and/or around the wire guide 308.

The second contact tip 314 includes a first bore 1310 having a firstdiameter. The electrode wire 114 makes electrical contact with the firstbore 1310. The example second contact tip 314 may also have a second,larger bore 1312 on a rear side of the contact tip 314 from the firstbore 1310. The length of the second bore 1312 may be selected to controla contact length of the first bore 1310.

As illustrated in FIG. 10 , the example contact tip 314 may have aninsert 1012 inserted within the first bore 1310 to improve contact withthe electrode wire 114, improve current transfer with the electrode wire114, and/or improve mechanical strength at operating temperatures.

FIGS. 14A and 14B illustrate views of the example diffuser 310 of FIGS.3 and 10 . As discussed above with reference to FIG. 10 , the diffuser310 includes two sets of exterior threads for installation into thediffuser insulator 304 and the cooling body 602, and a set of interiorthreads for installation of the first contact tip 306 into the diffuser310. The diffuser 310 includes gas outlets 1402 to enable the flow ofgas from the inner diameter 1010 of the cooling body 602 to the nozzle302 for output to the weld.

FIG. 15A illustrates a conventional robotic welding torch 1500 having afirst tool center point distance and torch neck angle. FIG. 15Billustrates an example implementation of the liquid-cooled welding torch200 of FIG. 2 configured to replace the conventional torch 1500 of FIG.15A while maintaining a same tool center point distance and torch neckangle.

The tool center point distance 1502 of the conventional torch 1500 is afunction of a stickout distance 1504, a nozzle length 1506, a nozzleangle 1508, a neck bend angle 1510, a tool center point area 1512, and aspacer width 1514. The tool center point area 1512 (e.g., Area_(TCP)) isdefined using Equation 1 below:

Area_(TCP)=0.5*((TCP−spacer width 1514)²*TAN(nozzle angle1508)+((TCP−spacer width 1514)−(nozzle length 1506+stickout1504)*COS(nozzle angle 1508))²*(TAN(nozzle angle 1508−neck bend angle1510)−1))   (Equation 1)

The example welding assembly 202 described above with reference to FIGS.10, 11A-11C, 12A, 12B, 13A-13C, 14A, and/or 14B may have a same nozzlelength 1506 as conventional nozzles. In other examples, the weldingassembly 202 may require a longer nozzle 302 than a nozzle of theconventional torch. In some examples, such as the welding torchdescribed below with reference to FIGS. 19-23 , the welding assembly mayhave a nozzle that is shorter than conventional nozzles. However, thelength of the example torch neck 1002 and/or the length and/or one ormore dimensions of the example mounting assembly 204 may be adjusted tocompensate for differences in the nozzle length.

Using the example welding assembly 202 disclosed herein, the exampleliquid-cooled welding torch 200 may be dimensioned to be a replacementfor any standard tool center point distance (e.g., 350 mm, 400 mm, 450mm, 500 mm, etc.) and/or torch neck angle (e.g., 0 degree, 22 degree, 35degree, 45 degree, etc.) to maintain the same TCP, torch neck angle, andtool center point area after replacement. In other words, disclosedexample welding assemblies 202 and/or liquid-cooled welding torches 200may be used as replacements for conventional robotic weld torches suchthat a robot on which the replacement occurs does not requirereprogramming or recalibration of new tool center point(s) or torch neckangle(s). After replacement of the conventional welding torch withdisclosed example liquid-cooled welding torches, the robot subject toreplacement is capable of higher deposition rates, improved weldingstarts, and/or other advantages over conventional welding torches. As aresult, reprogramming of welding voltages, currents, and/or torch travelspeeds may be performed to realize the advantages of the liquid-cooledwelding torch 200 for previously programmed welding tasks.

In addition to the tool center point distance 1502, the stickoutdistance 1504, the nozzle length 1506, the nozzle angle 1508, the neckbend angle 1510, the tool center point area 1512, and the spacer width1514 dimensions of the conventional welding torch 1500, the examplewelding torch 200 includes a preheat distance 1516 within the nozzle.The nozzle length 1506 is subdivided into the stickout distance 1504,the preheat distance 1516, and a neck-to-contact tip length 1518. Theconventional torch 1500 may be considered to have a preheat distance1516 of 0. By replacing a conventional weld torch 1500 with a weld torch200 having substantially the same tool center point distance 1502, thestickout distance 1504, the nozzle length 1506, the nozzle angle 1508,the neck bend angle 1510, and the tool center point area 1512, thereplacement reduces the programming needed to avoid an increased risk ofcollisions.

Tables 1 and 2 below illustrates example comparisons of the dimensions1502-1516 for two example tool center point distances 1502, 350 mm and400 mm.

TABLE 1 350 mm TCP Dimensions for Conventional and Disclosed examplewelding torches Neck-to-contact Nozzle Nozzle Neck TCP TCP TCP StickoutPreheat tip length length angle angle area # (mm) (in) (in) (in) (in)(in) (deg.) (deg.) (sq. in.) 1 350 13.78 0.59 0.00 4.33 4.92 45 22 51.592 350 13.78 0.75 3.29 1.78 5.82 45 22 54.61 3 350 13.78 0.75 2.40 1.784.93 45 22 51.61

TABLE 2 400 mm TCP Dimensions for Conventional and Disclosed examplewelding torches Neck-to-contact Nozzle Nozzle Neck TCP TCP TCP StickoutPreheat tip length length angle angle area # (mm) (in) (in) (in) (in)(in) (deg.) (deg.) (sq. in.) 4 400 15.75 0.59 0.00 4.33 4.92 45 22 66.445 400 15.75 0.75 3.29 1.78 5.82 45 22 70.17 6 400 15.75 0.75 2.40 1.784.93 45 22 66.46

A welding torch having a preheat length of 3.29 inches (e.g., torches 2and 5 of Tables 1 and 2 above) may be used with an air-cooled torch. Awelding torch having a preheat length of 2.40 inches results in a nozzlelength 1506 and TCP area 1512 of a welding torch 200 that substantiallymatch the nozzle length and TCP area 1512 of the conventional torch1500. However, the current density may increase enough to require anincrease in the radius of the welding assembly 202 (e.g., increasedcomponents in the welding assembly 202) to continue to use air cooling(as in torches 2 and 5 of Tables 1 and 2). Additionally oralternatively, the preheat distance of 2.40 inches may be used with theexample liquid cooled welding torch 200 disclosed herein.

Any of the dimensions of Tables 1 and 2 (or similar dimensions) may beselected based on a specification of another of the dimensions. Forexample, the preheating length (and, thus, the dimensions of the weldingassembly) may be selected based on any of the TCP, the stickout, theneck-to-contact tip length, the nozzle length, the nozzle angle, theneck angle, and/or the TCP area. Additionally or alternatively, theneck-to-contact tip length is based on at least one of a nozzle length,a preheat distance, a nozzle angle, or a neck angle.

Preheat lengths 1516 that are longer than the 3.29 inches of theexamples of Tables 1 and 2 may result in a torch envelope that is largerthan the envelope of the conventional torches 1500 by more than anacceptable amount. Torches having an envelope that is excessively largemay require more robot programming to serve as a replacement for aconventional torch and/or has a higher chance of collision duringoperation. Additional programming and collisions are undesirable effectsof replacement, and disclosed examples reduce or prevent such effectswhile providing the benefits of electrode preheating at the weldingassembly 202.

While the example welding assembly 202 includes the first contact tip306 and the second contact tip 314 such that both of the contact tips306, 314 are on a distal end of the bend in the torch neck 1002, in someother examples the second contact tip 314 is on a proximal side of thebend in the torch neck 1002. Additionally or alternatively, a thirdcontact tip is further located on the proximal side of the bend in thetorch neck 1002 so that preheating occurs between the second contact tip314 (on either side of the bend) and the third contact tip (on theproximal side of the bend).

When the electrode wire 114 is heated beyond a particular temperature,the column strength of the electrode wire 114 may be reduced to a pointthat the heated electrode wire 114 can no longer be pushed around thebend in the torch neck 1002 without buckling. In some such examples, theliquid-cooled welding torch 200 is provided with a pull motor to assistthe push motor located in the wire feeder.

The bend in the torch neck 1002 may be provided with ceramic bearings toreduce the friction force between the wire liner 1004 and the electrodewire 114, which increases the temperature to which the electrode wire114 may be preheated before buckling becomes likely.

In some examples, the length between the first and second contact tips306, 314 (e.g., the preheat length) is adjustable to change the lengthof the electrode wire 114 that is being preheated. As the preheat lengthincreases, the energy added to the electrode wire 114 is increased perunit of current. To change the preheat length, one or both of thecontact tips 306, 314 may be configured to be translated in the axialdirection via manual and/or automatic methods.

Using the second contact tip 314 as an example, the second contact tip314 may be threaded into an intermediate device between the secondcontact tip 314 and the torch neck 1002. The intermediate device may beautomatically rotated (e.g., with a motor coupled to the contact tip)and/or manually rotated (e.g., with a thumb wheel or other deviceconfigured to cause rotation in the contact tip) while limiting rotationof the second contact tip 314, which causes the threads of the secondcontact tip 314 to carry the second contact tip 314 toward or away fromthe first contact tip 306.

Additionally or alternatively, the first and/or second contact tips 306,314 may be configured to be reversible to change the preheat length. Forexample, if the first contact tip 306 has a contact location with theelectrode wire 114 that is closer than a midpoint of the first contacttip 306 to the second contact tip 314, reversing the first contact tip306 changes the contact location with the electrode wire 114 and extendsthe preheat length. In some examples, different contact tips havedifferent contact points, so that changing contact tips changes thepreheat length. In some other examples, the welding assembly 202 may bereplaced with a different welding assembly that has a different preheatlength such as different spacing between the contact tips 306, 314(which may require a different robotic program to be run that accountsfor a different nozzle length).

The change in preheat length may be automatically controlled based on,for example, a temperature of the electrode wire 114 and/or based on adesired preheat level or heat input to the weld specified by a user. Insome examples, a current controlled control loop is used to controlpreheat current when the preheat length is automatically adjustable.

The power and liquid transfer assembly 216 is attached to the torch body338 on a side of the torch body 338 opposite the mounting assembly 204,or opposite a direction of the bend in the torch neck 1002. Because thepower and liquid transfer assembly 216 increasing a volume of the torch200, locating the power and liquid transfer assembly 216 opposite themounting assembly 204 and/or opposite a direction of the bend in thetorch neck 1002 may reduce the chances of collision with a workpiecewhen using the same program with the replacement preheating weld torch200 as used with a conventional weld torch.

In still other examples, the welding assembly 202 may be provided with awire oscillator to cause physical oscillation or weave at a tip of theelectrode wire 114. An example implementation of the wire oscillatorthat may be used to provide wire oscillation is described in U.S. Pat.No. 4,295,031. Using both the wire oscillator and the contact tips 306,314, disclosed example welding torches may provide both wire oscillationand resistive preheating to a weld to further improve deposition ratesand weld quality.

FIG. 16 is a cross section of an example welding cable 1600 that may beused to provide cooling liquid, welding current, and preheating currentto a welding torch, and to carry cooling liquid away from the weldingtorch. The example welding cable 1600 may be used instead of the liquidcooling assemblies 208, 210, in cases in which the first contact tip 306is part of the preheating circuit and the welding circuit.

The welding cable 1600 is a coaxial-type welding cable, in which theelectrode wire 114 is fed through a wire guide 1602. The wire guide 1602is surrounded by a jacket 1604. A first conductor 1606 provides a firstelectrical path for preheating current, or welding current andpreheating current. The first conductor 1606 may be, for example, acopper sheath or webbing rated to conduct welding current. The firstconductor 1606 is surrounded by a jacket 1608.

A second conductor 1610 provides a second electrical path for preheatcurrent, or welding current and preheating current. In the example ofFIG. 16 , a first one of the first conductor 1606 or the secondconductor 1610 provides a path for the preheating current and is coupledto a preheating power supply. The second conductor 1610 is surrounded bya jacket 1612. In some examples, another protective layer may be presentoutside of the jacket 1612 to protect the welding cable 1600 fromdamage. In some examples, the jacket 1612 provides both physical andelectrical protection to the cable 1600.

An annulus 1614 between the jacket 1604 and the first conductor 1606and/or the jacket 1608 conducts cooling liquid in a first direction(e.g., from a liquid cooler to the welding torch, from the welding torchto the liquid cooler). An annulus 1616 between the jacket 1608 and thesecond conductor 1610 and/or the jacket 1612 conducts the cooling liquidin a second direction opposite the liquid flow direction in the annulus1614.

FIG. 17 illustrates a functional diagram of an example welding system1700 including the example welding torch 200 of FIG. 2 , and which maybe used with the welding system 100 of FIG. 1 . The welding system 1700includes the weld torch 200 having the first contact tip 306 and asecond contact tip 314. The system 1700 further includes the electrodewire 114 fed from a wire feeder 1702 having a wire drive 1704 and a wirespool 1706, a preheating power supply 1708, and a welding power supply1710. The system 1700 is illustrated in operation as producing a weldingarc 1712 between the electrode wire 114 and a workpiece 106.

In operation, the electrode wire 114 passes from the wire spool 1706through the second contact tip 314 and the first contact tip 306,between which the preheating power supply 1708 generates a preheatingcurrent to heat the electrode wire 114. Specifically, in theconfiguration shown in FIG. 17 , the preheating current enters theelectrode wire 114 via the second contact tip 314 (e.g., via the wiredrive 1704 and/or the torch neck 1002 of FIG. 10 ) and exits via thefirst contact tip 306. At the first contact tip 306, a welding currentmay also enter the electrode wire 114 (e.g., via the liquid coolingassemblies 208 and 212, and/or 210 and 214. The welding current isgenerated, or otherwise provided by, the welding power supply 1710. Thewelding current exits the electrode wire 114 via the workpiece 106,which in turn generates the welding arc 1712. When the electrode wire114 makes contact with a target metal workpiece 106, an electricalcircuit is completed and the welding current flows through the electrodewire 114, across the metal work piece(s) 106, and returns to the weldingpower supply 1710. The welding current causes the electrode wire 114 andthe parent metal of the work piece(s) 106 in contact with the electrodewire 114 to melt, thereby joining the work pieces as the meltsolidifies. By preheating the electrode wire 114, a welding arc 1712 maybe generated with drastically reduced arc energy. Generally speaking,the preheating current is proportional to the distance between thecontact tips 306, 314 and the electrode wire 114 size.

The welding current is generated, or otherwise provided by, a weldingpower supply 1710, while the preheating current is generated, orotherwise provided by, the preheating power supply 1708. The preheatingpower supply 1708 and the welding power supply 1710 may ultimately sharea common power source (e.g., a common generator or line currentconnection), but the current from the common power source is converted,inverted, and/or regulated to yield the two separate currents—thepreheating current and the welding current. For instance, the preheatoperation may be facilitated with a single power source and associatedconverter circuitry, in which case three leads may extend from a singlepower source.

During operation, the system 1700 establishes a welding circuit toconduct welding current from the welding power supply 1710 to the firstcontact tip 306 via the liquid cooling assemblies 208 and 212 and/or 210and 214, and returns to the power supply 1710 via the welding arc 1712,the workpiece 106, and a work lead 1718. To enable connection betweenthe welding power supply 1710 and the first contact tip 306 and theworkpiece 106, the welding power supply 1710 includes terminals 1720,1722 (e.g., a positive terminal and a negative terminal).

During operation, the preheating power supply establishes a preheatingcircuit to conduct preheating current through a section 1726 of theelectrode wire 114. To enable connection between the preheating powersupply 1708 and the contact tips 306, 314, the preheating power supply1708 includes terminals 1728, 1730. The preheating current flows fromthe welding power supply 1710 to the second contact tip 314 (e.g., viathe torch neck 1002), the section 1726 of the electrode wire 114, thefirst contact tip 306, and returns to the preheating power supply 1708via a cable 1732 connecting the terminal 1720 of the welding powersupply 1710 to the terminal 1730 of the preheating power supply 1708.

Because the preheating current path is superimposed with the weldingcurrent path over the connection between the first contact tip 306 andthe power supplies 1708, 1710, the cable 1732 may enable a morecost-effective single connection between the first contact tip 306 andthe power supplies 1708, 1710 (e.g., a single cable) than providingseparate connections for the welding current to the first contact tip306 and for the preheating current to the first contact tip 306. Inother examples, the terminal 1730 of the preheating power supply 1708 isconnected to the first contact tip 306 via a separate path than the pathbetween the first contact tip 306 and the welding power supply 1710. Forexample, the welding current may be conducted via the liquid coolingassemblies 208 and 212 while the preheating current is conducted via theliquid cooling assemblies 210 and 214 (or vice versa).

In some examples, the welding torch may include a push-pull wire feedsystem by including a feed motor located at or near the weld torch topull the electrode wire 114. In some examples, the inclusion of thepulling feed motor enables the portion of the electrode wire 114 that ispreheated to a different location along the wire feed path than in theexamples of FIGS. 2, 3, and 10. For example, the second contact tip 314may be moved into the neck 1002 (e.g., prior to the bend in the torchneck 1002 in the feed direction of the electrode wire 114) and/or in thetorch body (e.g., the mounting assembly 204 of FIG. 2 ) and/or multiplecontact tips may be positioned at locations along the length of theelectrode wire 114 to provide a preheating circuit that is separate fromthe welding circuit (e.g., does not share a same contact tip with thewelding circuit) and/or provides an additional preheating circuit (e.g.,a first preheating current applied to a first portion of the electrodewire 114 and a second preheat current applied to a second portion of thepreheating wire). In some examples, the idler roller of a push-pull wirefeed system may function as a contact tip to conduct preheating current.By moving all or a portion of the preheating circuit to the wire sourceside of the bend in the torch neck 1002 (e.g., the side of the bendcloser to the wire spool in the electrode feed path), the size of thewelding assembly may be reduced, the preheat length may be increased,and/or the preheating current may be reduced. Reduction in the size ofthe welding assembly and reduction in the preheating current enablestorch dimensions that are closer to those of conventional, non-resistivepreheating torches, further improving the ease of replacement ofconventional torches with torches providing resistive preheating.

FIG. 18 is a block diagram of an example implementation of the powersupplies 1708, 1710 of FIG. 17 . The example power supply 1708, 1710powers, controls, and supplies consumables to a welding application. Insome examples, the power supply 1708, 1710 directly supplies input powerto the welding tool 108. In the illustrated example, the power supply1708, 1710 is configured to supply power to welding operations and/orpreheating operations. The example power supply 1708, 1710 also providespower to a wire feeder to supply the electrode wire 114 to the weldingtool 108 for various welding applications (e.g., GMAW welding, flux corearc welding (FCAW)).

The power supply 1708, 1710 receives primary power 1808 (e.g., from theAC power grid, an engine/generator set, a battery, or other energygenerating or storage devices, or a combination thereof), conditions theprimary power, and provides an output power to one or more weldingdevices and/or preheating devices in accordance with demands of thesystem. The primary power 1808 may be supplied from an offsite location(e.g., the primary power may originate from the power grid). The powersupply 1708, 1710 includes a power converter 1810, which may includetransformers, rectifiers, switches, and so forth, capable of convertingthe AC input power to AC and/or DC output power as dictated by thedemands of the system (e.g., particular welding processes and regimes).The power converter 1810 converts input power (e.g., the primary power1808) to welding-type power based on a weld voltage setpoint and outputsthe welding-type power via a weld circuit.

In some examples, the power converter 1810 is configured to convert theprimary power 1808 to both welding-type power and auxiliary poweroutputs. However, in other examples, the power converter 1810 is adaptedto convert primary power only to a weld power output, and a separateauxiliary converter is provided to convert primary power to auxiliarypower. In some other examples, the power supply 1708, 1710 receives aconverted auxiliary power output directly from a wall outlet. Anysuitable power conversion system or mechanism may be employed by thepower supply 1708, 1710 to generate and supply both weld and auxiliarypower.

The power supply 1708, 1710 includes a controller 1812 to control theoperation of the power supply 1708, 1710. The power supply 1708, 1710also includes a user interface 1814. The controller 1812 receives inputfrom the user interface 1814, through which a user may choose a processand/or input desired parameters (e.g., voltages, currents, particularpulsed or non-pulsed welding regimes, and so forth). The user interface1814 may receive inputs using any input device, such as via a keypad,keyboard, buttons, touch screen, voice activation system, wirelessdevice, etc. Furthermore, the controller 1812 controls operatingparameters based on input by the user as well as based on other currentoperating parameters. Specifically, the user interface 1814 may includea display 1816 for presenting, showing, or indicating, information to anoperator. The controller 1812 may also include interface circuitry forcommunicating data to other devices in the system, such as the wirefeeder. For example, in some situations, the power supply 1708, 1710wirelessly communicates with other welding devices within the weldingsystem. Further, in some situations, the power supply 1708, 1710communicates with other welding devices using a wired connection, suchas by using a network interface controller (NIC) to communicate data viaa network (e.g., ETHERNET, 10baseT, 10base100, etc.). In the example ofFIG. 18 , the controller 1812 communicates with the wire feeder via theweld circuit via a communications transceiver 1818.

The controller 1812 includes at least one controller or processor 1820that controls the operations of the welding power supply 1802. Thecontroller 1812 receives and processes multiple inputs associated withthe performance and demands of the system. The processor 1820 mayinclude one or more microprocessors, such as one or more“general-purpose” microprocessors, one or more special-purposemicroprocessors and/or ASICS, and/or any other type of processingdevice. For example, the processor 1820 may include one or more digitalsignal processors (DSPs).

The example controller 1812 includes one or more storage device(s) 1823and one or more memory device(s) 1824. The storage device(s) 1823 (e.g.,nonvolatile storage) may include ROM, flash memory, a hard drive, and/orany other suitable optical, magnetic, and/or solid-state storage medium,and/or a combination thereof. The storage device 1823 stores data (e.g.,data corresponding to a welding application), instructions (e.g.,software or firmware to perform welding processes), and/or any otherappropriate data. Examples of stored data for a welding applicationinclude an attitude (e.g., orientation) of a welding torch, a distancebetween the contact tip and a workpiece, a voltage, a current, weldingdevice settings, and so forth.

The memory device 1824 may include a volatile memory, such as randomaccess memory (RAM), and/or a nonvolatile memory, such as read-onlymemory (ROM). The memory device 1824 and/or the storage device(s) 1823may store a variety of information and may be used for various purposes.For example, the memory device 1824 and/or the storage device(s) 1823may store processor executable instructions 1825 (e.g., firmware orsoftware) for the processor 1820 to execute. In addition, one or morecontrol regimes for various welding processes, along with associatedsettings and parameters, may be stored in the storage device 1823 and/ormemory device 1824, along with code configured to provide a specificoutput (e.g., initiate wire feed, enable gas flow, capture weldingcurrent data, detect short circuit parameters, determine amount ofspatter) during operation.

In some examples, the welding power flows from the power converter 1810through a weld cable 1826. The example weld cable 1826 is attachable anddetachable from weld studs at each of the power supply 1708, 1710 (e.g.,to enable ease of replacement of the weld cable 1826 in case of wear ordamage). Furthermore, in some examples, welding data is provided withthe weld cable 1826 such that welding power and weld data are providedand transmitted together over the weld cable 1826. The communicationstransceiver 1818 is communicatively coupled to the weld cable 1826 tocommunicate (e.g., send/receive) data over the weld cable 1826. Thecommunications transceiver 1818 may be implemented based on varioustypes of power line communications methods and techniques. For example,the communications transceiver 1818 may utilize IEEE standard P1901.2 toprovide data communications over the weld cable 1826. In this manner,the weld cable 1826 may be utilized to provide welding power from thepower supply 1708, 1710 to the wire feeder and the welding tool 108.Additionally or alternatively, the weld cable 1826 may be used totransmit and/or receive data communications to/from the wire feeder andthe welding tool 108. The communications transceiver 1818 iscommunicatively coupled to the weld cable 1826, for example, via cabledata couplers 1827, to characterize the weld cable 1826, as described inmore detail below. The cable data coupler 1827 may be, for example, avoltage or current sensor.

In some examples, the power supply 1708, 1710 includes or is implementedin a wire feeder.

The example communications transceiver 1818 includes a receiver circuit1821 and a transmitter circuit 1822. Generally, the receiver circuit1821 receives data transmitted by the wire feeder via the weld cable1826 and the transmitter circuit 1822 transmits data to the wire feedervia the weld cable 1826. As described in more detail below, thecommunications transceiver 1818 enables remote configuration of thepower supply 1708, 1710 from the location of the wire feeder and/orcompensation of weld voltages by the power supply 1708, 1710 using weldvoltage feedback information transmitted by the wire feeder 104. In someexamples, the receiver circuit 1821 receives communication(s) via theweld circuit while weld current is flowing through the weld circuit(e.g., during a welding-type operation) and/or after the weld currenthas stopped flowing through the weld circuit (e.g., after a welding-typeoperation). Examples of such communications include weld voltagefeedback information measured at a device that is remote from the powersupply 1708, 1710 (e.g., the wire feeder) while the weld current isflowing through the weld circuit

Example implementations of the communications transceiver 1818 aredescribed in U.S. Pat. No. 9,012,807. The entirety of U.S. Pat. No.9,012,807 is incorporated herein by reference. However, otherimplementations of the communications transceiver 1818 may be used.

The example wire feeder 104 also includes a communications transceiver1819, which may be similar or identical in construction and/or functionas the communications transceiver 1818.

In some examples, a gas supply 1828 provides shielding gases, such asargon, helium, carbon dioxide, and so forth, depending upon the weldingapplication. The shielding gas flows to a valve 1830, which controls theflow of gas, and if desired, may be selected to allow for modulating orregulating the amount of gas supplied to a welding application. Thevalve 1830 may be opened, closed, or otherwise operated by thecontroller 1812 to enable, inhibit, or control gas flow (e.g., shieldinggas) through the valve 1830. Shielding gas exits the valve 1830 andflows through a cable 1832 (which in some implementations may bepackaged with the welding power output) to the wire feeder whichprovides the shielding gas to the welding application. In some examples,the power supply 1708, 1710 does not include the gas supply 1828, thevalve 1830, and/or the cable 1832.

FIG. 19 illustrates another example liquid-cooled welding torch 1900.Like the torch 200 of FIGS. 2-14B, the example liquid-cooled weldingtorch 1900 resistively preheats an electrode wire 114 via multiplecontact points (e.g., contact tips) in the torch 1900.

The torch 1900 of FIG. 19 includes a welding assembly 1902, a mountingassembly 1904, a weld cable 1906, liquid cooling assemblies 1908, 1910,1912, 1914, and a power and liquid transfer assembly 1916. The exampleliquid-cooled welding torch 1900 may be used to replace conventionalrobotic welding torches with resistive preheating-enabled weldingtorches having a same tool center point (TCP).

The welding assembly 1902 receives weld current and preheating current,conducts the weld current to the electrode wire 114, and conducts thepreheating current through a portion of the electrode wire 114. Theexample welding assembly 1902 is liquid-cooled by liquid provided viathe liquid cooling assemblies 1908-214. The example welding assembly1902 of FIG. 19 receives the weld current via one or more of the weldcable 1906, the liquid cooling assemblies 1908 and 1912, and/or theliquid cooling assemblies 1910 and 1914. Because the workpiece providesthe return path for the weld current to the power supply, no return pathis provided via the weld cable 1906 or the liquid cooling assemblies1908. The weld cable 1906 is a air-cooled (or gas-cooled) cable.However, the weld cable 1906 may also be liquid-cooled.

The example welding assembly 1902 receives the preheating current viathe weld cable 1906, the liquid cooling assemblies 1908 and 1912, and/orthe liquid cooling assemblies 1910 and 1914. In the example of FIG. 19 ,the weld current is conducted via a different one of the weld cable1906, the liquid cooling assemblies 1908 and 1912, or the liquid coolingassemblies 1910 and 1914 than the preheating current that has the samepolarity (i.e., current flow direction). The welding assembly 1902conducts the preheating current through a section of the electrode wire114 to heat the electrode wire via resistive heating (e.g., FR heating).The preheat current then returns to a preheating power supply via adifferent one of weld cable 1906, the liquid cooling assemblies 1908 and1912, or the liquid cooling assemblies 1910 and 1914 to complete apreheating circuit.

In the example of FIG. 19 , the weld current path, the preheatingcurrent supply path, and the preheating current return path may all bedifferent ones of the weld cable 1906, the liquid cooling assemblies1908 and 1912, and the liquid cooling assemblies 1910 and 1914. In someexamples, the weld current path may be superimposed with the preheatingcurrent supply path or the preheating current return path to reduce thenet current in the conductor. For example, if the weld current is 300 Aand the preheating current is 100 A, the weld current and the preheatingcurrent may be superimposed to result in a net current of 1900 A.

As described in more detail below, the welding assembly 1902 and theliquid cooling assemblies 1912, 1914 may be separated from the remainderof the liquid-cooled welding torch 1900 via the power and liquidtransfer assembly 1916, and may be simultaneously separated from themounting assembly 1904.

FIG. 20 is an exploded view of the example welding assembly 1902 of thewelding torch 1900 of FIG. 19 . The welding assembly 1902 includes afront portion 2002 and a rear portion 2004. FIG. 21 is a cross-sectionalplan view of the example welding assembly 1902 of FIG. 19 in which thefront portion 2002 is coupled to the rear portion 2004. As described inmore detail below, the front portion 2002 is detachable from the rearportion to enable access to a rear contact tip 2006 (e.g., a preheatingcontact tip).

The front portion 2002 includes a nozzle 2008, a nozzle insulator 2010,a front contact tip 2012, a diffuser 2014, a wire guide 2016, a coolingbody 2018, a hand nut 2020, and a hand nut insulator 2022. The rearportion 2004 includes a valve assembly 2024, a valve assembly insulator2026, and a valve assembly housing 2028.

The example hand nut 2020 secures the cooling body 2018, and thecomponents 2008-2016 connected to the cooling body 2018, to the rearportion 2004. In the example of FIG. 20 , the hand nut 2020 has internalscrew threads to be threaded onto external screw threads 2030 of thevalve assembly 2024. A tapered edge 2032 of the hand nut 2020 mates witha shoulder of the cooling body 2018 to force the cooling body 2018toward the valve assembly 2024. The hand nut insulator 2022 electricallyinsulates the hand nut to reduce or prevent an operator contacting weldvoltage and/or preheating voltage via the hand nut 2020.

The example valve assembly 2024 includes fluid valves 2034 a, 2034 bpositioned within fluid channels 2036 a, 2036 b, respectively. The fluidchannels 2036 a, 2036 b are in fluid communication with the liquidcooling assemblies 1912, 1914 to circulate fluid through the weldingassembly 1902. The example valves 2034 a, 2034 b are Shrader valves thatcut off fluid flow when the valves are not actuated. To actuate thevalves, the example cooling body 2018 includes valve actuators 2038 a,2038 b, which are located within channels 2040 a, 2040 b of the coolingbody 2018. The valve actuators 2038 a, 2038 b actuate the valves 2034 a,2034 b when the front portion 2002 (including the cooling body 2018) issecured to the rear portion 2004.

When the valves are actuated, the cooling body 2018 is in fluidcommunication with the liquid cooling assemblies 1912, 1914. The examplecooling body 2018 includes one or more internal channels to direct fluidfrom one of the valve actuators 2038 a, 2038 b to a second one of thevalve actuators 2038 a, 2038 b. In other words, one of the valveactuators 2038 a, 2038 b is an inlet to the channel(s) 2102 in thecooling body 2018 from one of the liquid cooling assemblies 1912, 1914and the other of the valve actuators 2038 a, 2038 b is an outlet fromthe channel(s) 2102 to the other of the liquid cooling assemblies 1912,1914. The example channels 2102 run circumferentially within the coolingbody 2018 between the valve actuators 2038 a, 2038 b to transfer heatfrom the nozzle 2008 to the fluid within the channels 2102.

The example nozzle 2008 includes internal threads 2104 that couple thenozzle 2008 to a threaded ring 2042 coupled to an exterior of thecooling body 2018. When coupled, heat from the nozzle 2008 istransferred to the cooling body 2018 for further dissipation to thecooling liquid.

When secured (e.g., threaded together), the cooling body 2018 and thevalve assembly 2024 are in electrical contact to transfer weldingcurrent and/or preheating current with the front contact tip 2012 viathe diffuser 2014. The welding current and/or preheating current areconducted via one or more of the liquid cooling assemblies 1912, 1914.For example, one or both of the liquid cooling assemblies 1912, 1914include a conductor layer electrically coupled to the front contact tip2012 via the diffuser 2014, the cooling body 2018, and the valveassembly 2024. Preheating current is conducted to the rear contact tip2006 from the weld cable 1906 via a torch neck 2044, which includes oneor more layers of conductors, a wire liner to transfer the electrodewire 114, and an annulus to provide gas flow to the weld assembly 1902for output to the weld via the diffuser 2014.

As illustrated in FIG. 20 , the liquid cooling assemblies 1912, 1914 maybe secured to the torch neck 2044 via bracket 2046 or other attachmenttechnique.

The example wire guide 2016 may be similar or identical to the wireguide 308 of FIG. 3 . The wire guide 2016 is held within a bore in thediffuser 2014. The nozzle insulator 2010 electrically and thermallyinsulates the nozzle 2008 from the front contact tip 2012 and thediffuser 2014. The nozzle 2008 is electrically insulated from thecooling body 2018 by one or more additional electrical insulator(s) 2110located on the cooling body 2018. The example electrical insulator(s)2110 may be thermally conductive to conduct heat from the nozzle 2008 tothe cooling body 2018. Polyether ether ketone (PEEK) and/or otherthermoplastics may be used to implement the example electricalinsulator(s) 2110.

The example cooling body 2018 may include any number of electricalinsulators and/or fluid seals to enable conduction of current to thediffuser 2014, reduce or prevent conduction of current to unneeded orundesired components (e.g., exterior components), and/or to reduce orprevent fluid leaks from the cooling body 2018. In the example of FIG.21 , the cooling body 2018 includes an inner body 2106 defining thechannel(s) 2102 and a cover 2108 configured to enclose the channels2102.

The example rear contact tip 2006 may be similar or identical to thesecond contact tip 314 of FIGS. 3 and 13A-13C.

FIG. 22 is a cross-sectional plan view of the example power and liquidtransfer assembly 1916 of FIG. 19 . FIG. 23 is a partially explodedelevation view of the example power and liquid transfer assembly 1916 ofFIG. 19 .

The example power and liquid transfer assembly 1916 is similar to thepower and liquid transfer assembly 216 of FIGS. 2, 3, and 8 , in thatthe power and liquid transfer assembly 1916 includes multiple liquidtransfer valves, corresponding valve actuators, and one or moreelectrical power transfer sockets, and in that the power and liquidtransfer assembly 1916 enables disconnection of the liquid coolingassemblies 1912, 1914 from the power and liquid transfer assembly 1916and cuts off fluid transfer in response to disconnection.

The example power and liquid transfer assembly 1916 is coupled to theliquid cooling assemblies 1908, 1910, which provide supply and returnlines for the cooling liquid to a liquid cooler. The example liquidcooling assembly 1908 includes an internal conductor 2202 to conductwelding current (e.g., to the welding power supply 1710 of FIG. 17 )and/or preheating current (e.g., to the preheating power supply 1708).The conductor 2202 is in electrical contact with a socket 2204, whichpermits fluid to flow from an exterior of the socket 2204 to an interiorof the socket 2204, into which a fluid fitting 2206 of the power andliquid transfer assembly 1916 is fitted to make a fluid connection withthe liquid cooling assembly 1908 and electrical contact with the socket2204. In the example of FIG. 22 , the liquid cooling assembly 1910 onlyincludes tubing to transfer liquid, and does not include an internalconductor or a socket. In other examples, the liquid cooling assembly1910 also includes a conductor and has a construction similar oridentical to the liquid cooling assembly 1908.

Each of the example liquid cooling channels of the power and liquidtransfer assembly 1916 includes a liquid shutoff valve 2208 a, 2208 bwithin a fluid socket 2209 a, 2209 b. The channel coupled to the liquidcooling assembly 1908 (e.g., carrying current and liquid) includes apower transfer socket 2210. The channel coupled to the liquid coolingassembly 1910 (e.g., carrying only liquid) may include a non-conductivesocket 2212 having similar, the same, or different dimensions as thepower transfer socket 2210.

The power cable socket 2210 receives a power connector pin 2214 of theliquid cooling assembly 1912 to transfer cooling liquid and weldingcurrent and/or preheating current to the liquid cooling assembly 1912.The nonconductive socket 2212 likewise receives a power connector pin orother pin corresponding to the dimensions of the socket 2212. The powertransfer socket 2210 enables insertion of the power connector pin 2214,and transfers current to and/or from an inserted power connector pin2214. An example power transfer socket that may be used to implement thepower transfer socket 2210 is a PowerBud® power contact, sold by MethodeElectronics, Inc., which provides multiple contact points between thepower transfer socket and an inserted power connector pin 2214.

The liquid shutoff valves 2208 a, 2208 b selectively permit flow ofliquid from liquid cooling assemblies 1908, 1910 to the sockets 2210,2212 and to a connected liquid cooling assembly 1912, 1914. The exampleliquid shutoff valves 2208 a, 2208 b are Schrader valves. However, othertypes of valves may be used to implement the liquid shutoff valves 2208a, 2208 b. When a power connector pin 2214, 2216 is inserted (e.g.,fully inserted) into the sockets 2210, 2212, the power connector pin2214, 2216 displaces (e.g., unseats) a stem 2218 from a core 2220 of thevalve 2208 a, 2208 b, which permits liquid to flow to and/or from thehose liquid cooling assemblies 1908-1914. When the power connector pins2214, 2216 are removed or partially removed, the stems 2218 are forcedback into the cores 2220 and stop flow of liquid.

A hose 2222 of the liquid cooling assemblies 1908 is coupled to thefluid socket 2209 a via a ferrule 2224. The example the example sockets2209 a, 2209 b and/or the hoses 2222 include hose barbs to secure thehoses 2222. However, other methods of securing the hose to the sockets2209 a, 2209 b may be used, such as clamps, compression fittings, or anyother hose fittings.

The example power and liquid transfer assembly 1916 may operate asdescribed above with reference to the power and liquid transfer assembly216 of FIG. 8 .

As illustrated in FIG. 23 , the liquid cooling assembles 1912, 1914 maybe secured to the power and liquid transfer assembly 1916 at leastpartly using a cover 2302 configured to prevent disconnection of thepower connector pins 2214, 2216 from the power and liquid transferassembly 1916. For example, the cover 2302 may include a shoulder and/orother features configured to prevent movement of the power connectorpins 2214, 2216 away from the power and liquid transfer assembly 1916.The cover 2302 may be secured by a fastener, such as a bolt, and/or anyother type of fastener or fastening technique.

While the present method and/or system has been described with referenceto certain implementations, it will be understood by those skilled inthe art that various changes may be made and equivalents may besubstituted without departing from the scope of the present methodand/or system. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the presentdisclosure without departing from its scope. For example, systems,blocks, and/or other components of disclosed examples may be combined,divided, re-arranged, and/or otherwise modified. Therefore, the presentmethod and/or system are not limited to the particular implementationsdisclosed. Instead, the present method and/or system will include allimplementations falling within the scope of the appended claims, bothliterally and under the doctrine of equivalents.

All documents cited herein, including journal articles or abstracts,published or corresponding U.S. or foreign patent applications, issuedor foreign patents, or any other documents are each entirelyincorporated by reference herein, including all data, tables, figures,and text presented in the cited documents.

What is claimed is:
 1. A contact tip, comprising: an inner boreconfigured to make direct physical contact with and conduct current to aconsumable welding electrode; screw threads on an exterior of thecontact tip, wherein the screw threads comprise longitudinal slots topermit welding gas to flow along an exterior of the contact tip; and ahead opposite the screw threads on an exterior of the contact tip toenable threading and dethreading of the contact tip.
 2. The contact tipas defined in claim 1, further comprising a second bore having a largerdiameter than the inner bore, the second bore configured to fit over awire liner of a welding torch and located on a rear side of the contacttip relative to the inner bore.
 3. The contact tip as defined in claim1, wherein the head comprises a hexagonal cross-section.
 4. The contacttip as defined in claim 1, wherein the inner bore extends through thehead.
 5. The contact tip as defined in claim 1, wherein the head has asmaller diameter than a major diameter of the screw threads.
 6. Thecontact tip as defined in claim 1, further comprising a contact insertin the inner bore and configured to contact the consumable weldingelectrode to conduct current between the consumable welding electrodeand the contact tip.
 7. A contact tip, comprising: an inner boreconfigured to make direct physical contact with and conduct current to aconsumable welding electrode; and screw threads on an exterior of thecontact tip, wherein the screw threads comprise longitudinal slots topermit welding gas to flow along an exterior of the contact tip.
 8. Thecontact tip as defined in claim 7, further comprising a second borehaving a larger diameter than the inner bore, the second bore configuredto fit over a wire liner of a welding torch and located on a rear sideof the contact tip relative to the inner bore.
 9. The contact tip asdefined in claim 7, further comprising a contact insert in the innerbore and configured to make the physical contact with the consumablewelding electrode to conduct current between the consumable weldingelectrode and the contact tip.